ASTM D6273-14

4.1 Federal regulations (49 CFR Part 192.625) state: “A combustible gas in a distribution line must contain a natural odorant or be odorized so that at a concentration in air of one-fifth of the lower explosive limit, the gas is readily detectable by a person with a normal sense of smell.” These regulations state further that “To assure the proper concentration of odorant with this section, each operator must conduct periodic sampling of combustible gases using an instrument capable of determining the percentage of gas in air at which the odor becomes readily detectable.” Additionally, a number of states have enacted legislation that requires natural gas to be odorized so that it is detectable at concentrations less than one fifth of the lower explosive limit. See Note 1. While regulations do not specify the exact method for determining compliance, it has been documented that compliance testing must be olfactory in nature.⁴

1.1 These test methods cover the procedures for determining the odor intensity of natural gas through the use of instruments that dilute and mix the sampled natural gas with air. The mixed gas stream is then sniffed by the operator for the purpose of determining the threshold detection level or the readily detection level, or both, for odorant in the natural gas stream.

1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.